[GitHub/mt8127/android_kernel_alcatel_ttab.git] / drivers / net / ppp / ppp_synctty.c

/*
 * PPP synchronous tty channel driver for Linux.
 *
 * This is a ppp channel driver that can be used with tty device drivers
 * that are frame oriented, such as synchronous HDLC devices.
 *
 * Complete PPP frames without encoding/decoding are exchanged between
 * the channel driver and the device driver.
 *
 * The async map IOCTL codes are implemented to keep the user mode
 * applications happy if they call them. Synchronous PPP does not use
 * the async maps.
 *
 * Copyright 1999 Paul Mackerras.
 *
 * Also touched by the grubby hands of Paul Fulghum paulkf@microgate.com
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 * This driver provides the encapsulation and framing for sending
 * and receiving PPP frames over sync serial lines.  It relies on
 * the generic PPP layer to give it frames to send and to process
 * received frames.  It implements the PPP line discipline.
 *
 * Part of the code in this driver was inspired by the old async-only
 * PPP driver, written by Michael Callahan and Al Longyear, and
 * subsequently hacked by Paul Mackerras.
 *
 * ==FILEVERSION 20040616==
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/tty.h>
#include <linux/netdevice.h>
#include <linux/poll.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-ioctl.h>
#include <linux/ppp_channel.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <asm/unaligned.h>
#include <asm/uaccess.h>

#define PPP_VERSION	"2.4.2"

/* Structure for storing local state. */
struct syncppp {
	struct tty_struct *tty;
	unsigned int	flags;
	unsigned int	rbits;
	int		mru;
	spinlock_t	xmit_lock;
	spinlock_t	recv_lock;
	unsigned long	xmit_flags;
	u32		xaccm[8];
	u32		raccm;
	unsigned int	bytes_sent;
	unsigned int	bytes_rcvd;

	struct sk_buff	*tpkt;
	unsigned long	last_xmit;

	struct sk_buff_head rqueue;

	struct tasklet_struct tsk;

	atomic_t	refcnt;
	struct completion dead_cmp;
	struct ppp_channel chan;	/* interface to generic ppp layer */
};

/* Bit numbers in xmit_flags */
#define XMIT_WAKEUP	0
#define XMIT_FULL	1

/* Bits in rbits */
#define SC_RCV_BITS	(SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)

#define PPPSYNC_MAX_RQLEN	32	/* arbitrary */

/*
 * Prototypes.
 */
static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *);
static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb);
static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
			  unsigned long arg);
static void ppp_sync_process(unsigned long arg);
static int ppp_sync_push(struct syncppp *ap);
static void ppp_sync_flush_output(struct syncppp *ap);
static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
			   char *flags, int count);

static const struct ppp_channel_ops sync_ops = {
	.start_xmit = ppp_sync_send,
	.ioctl      = ppp_sync_ioctl,
};

/*
 * Utility procedure to print a buffer in hex/ascii
 */
static void
ppp_print_buffer (const char *name, const __u8 *buf, int count)
{
	if (name != NULL)
		printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);

	print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, count);
}


/*
 * Routines implementing the synchronous PPP line discipline.
 */

/*
 * We have a potential race on dereferencing tty->disc_data,
 * because the tty layer provides no locking at all - thus one
 * cpu could be running ppp_synctty_receive while another
 * calls ppp_synctty_close, which zeroes tty->disc_data and
 * frees the memory that ppp_synctty_receive is using.  The best
 * way to fix this is to use a rwlock in the tty struct, but for now
 * we use a single global rwlock for all ttys in ppp line discipline.
 *
 * FIXME: Fixed in tty_io nowadays.
 */
static DEFINE_RWLOCK(disc_data_lock);

static struct syncppp *sp_get(struct tty_struct *tty)
{
	struct syncppp *ap;

	read_lock(&disc_data_lock);
	ap = tty->disc_data;
	if (ap != NULL)
		atomic_inc(&ap->refcnt);
	read_unlock(&disc_data_lock);
	return ap;
}

static void sp_put(struct syncppp *ap)
{
	if (atomic_dec_and_test(&ap->refcnt))
		complete(&ap->dead_cmp);
}

/*
 * Called when a tty is put into sync-PPP line discipline.
 */
static int
ppp_sync_open(struct tty_struct *tty)
{
	struct syncppp *ap;
	int err;
	int speed;

	if (tty->ops->write == NULL)
		return -EOPNOTSUPP;

	ap = kzalloc(sizeof(*ap), GFP_KERNEL);
	err = -ENOMEM;
	if (!ap)
		goto out;

	/* initialize the syncppp structure */
	ap->tty = tty;
	ap->mru = PPP_MRU;
	spin_lock_init(&ap->xmit_lock);
	spin_lock_init(&ap->recv_lock);
	ap->xaccm[0] = ~0U;
	ap->xaccm[3] = 0x60000000U;
	ap->raccm = ~0U;

	skb_queue_head_init(&ap->rqueue);
	tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);

	atomic_set(&ap->refcnt, 1);
	init_completion(&ap->dead_cmp);

	ap->chan.private = ap;
	ap->chan.ops = &sync_ops;
	ap->chan.mtu = PPP_MRU;
	ap->chan.hdrlen = 2;	/* for A/C bytes */
	speed = tty_get_baud_rate(tty);
	ap->chan.speed = speed;
	err = ppp_register_channel(&ap->chan);
	if (err)
		goto out_free;

	tty->disc_data = ap;
	tty->receive_room = 65536;
	return 0;

 out_free:
	kfree(ap);
 out:
	return err;
}

/*
 * Called when the tty is put into another line discipline
 * or it hangs up.  We have to wait for any cpu currently
 * executing in any of the other ppp_synctty_* routines to
 * finish before we can call ppp_unregister_channel and free
 * the syncppp struct.  This routine must be called from
 * process context, not interrupt or softirq context.
 */
static void
ppp_sync_close(struct tty_struct *tty)
{
	struct syncppp *ap;

	write_lock_irq(&disc_data_lock);
	ap = tty->disc_data;
	tty->disc_data = NULL;
	write_unlock_irq(&disc_data_lock);
	if (!ap)
		return;

	/*
	 * We have now ensured that nobody can start using ap from now
	 * on, but we have to wait for all existing users to finish.
	 * Note that ppp_unregister_channel ensures that no calls to
	 * our channel ops (i.e. ppp_sync_send/ioctl) are in progress
	 * by the time it returns.
	 */
	if (!atomic_dec_and_test(&ap->refcnt))
		wait_for_completion(&ap->dead_cmp);
	tasklet_kill(&ap->tsk);

	ppp_unregister_channel(&ap->chan);
	skb_queue_purge(&ap->rqueue);
	kfree_skb(ap->tpkt);
	kfree(ap);
}

/*
 * Called on tty hangup in process context.
 *
 * Wait for I/O to driver to complete and unregister PPP channel.
 * This is already done by the close routine, so just call that.
 */
static int ppp_sync_hangup(struct tty_struct *tty)
{
	ppp_sync_close(tty);
	return 0;
}

/*
 * Read does nothing - no data is ever available this way.
 * Pppd reads and writes packets via /dev/ppp instead.
 */
static ssize_t
ppp_sync_read(struct tty_struct *tty, struct file *file,
	       unsigned char __user *buf, size_t count)
{
	return -EAGAIN;
}

/*
 * Write on the tty does nothing, the packets all come in
 * from the ppp generic stuff.
 */
static ssize_t
ppp_sync_write(struct tty_struct *tty, struct file *file,
		const unsigned char *buf, size_t count)
{
	return -EAGAIN;
}

static int
ppp_synctty_ioctl(struct tty_struct *tty, struct file *file,
		  unsigned int cmd, unsigned long arg)
{
	struct syncppp *ap = sp_get(tty);
	int __user *p = (int __user *)arg;
	int err, val;

	if (!ap)
		return -ENXIO;
	err = -EFAULT;
	switch (cmd) {
	case PPPIOCGCHAN:
		err = -EFAULT;
		if (put_user(ppp_channel_index(&ap->chan), p))
			break;
		err = 0;
		break;

	case PPPIOCGUNIT:
		err = -EFAULT;
		if (put_user(ppp_unit_number(&ap->chan), p))
			break;
		err = 0;
		break;

	case TCFLSH:
		/* flush our buffers and the serial port's buffer */
		if (arg == TCIOFLUSH || arg == TCOFLUSH)
			ppp_sync_flush_output(ap);
		err = n_tty_ioctl_helper(tty, file, cmd, arg);
		break;

	case FIONREAD:
		val = 0;
		if (put_user(val, p))
			break;
		err = 0;
		break;

	default:
		err = tty_mode_ioctl(tty, file, cmd, arg);
		break;
	}

	sp_put(ap);
	return err;
}

/* No kernel lock - fine */
static unsigned int
ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
{
	return 0;
}

/* May sleep, don't call from interrupt level or with interrupts disabled */
static void
ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
		  char *cflags, int count)
{
	struct syncppp *ap = sp_get(tty);
	unsigned long flags;

	if (!ap)
		return;
	spin_lock_irqsave(&ap->recv_lock, flags);
	ppp_sync_input(ap, buf, cflags, count);
	spin_unlock_irqrestore(&ap->recv_lock, flags);
	if (!skb_queue_empty(&ap->rqueue))
		tasklet_schedule(&ap->tsk);
	sp_put(ap);
	tty_unthrottle(tty);
}

static void
ppp_sync_wakeup(struct tty_struct *tty)
{
	struct syncppp *ap = sp_get(tty);

	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
	if (!ap)
		return;
	set_bit(XMIT_WAKEUP, &ap->xmit_flags);
	tasklet_schedule(&ap->tsk);
	sp_put(ap);
}


static struct tty_ldisc_ops ppp_sync_ldisc = {
	.owner	= THIS_MODULE,
	.magic	= TTY_LDISC_MAGIC,
	.name	= "pppsync",
	.open	= ppp_sync_open,
	.close	= ppp_sync_close,
	.hangup	= ppp_sync_hangup,
	.read	= ppp_sync_read,
	.write	= ppp_sync_write,
	.ioctl	= ppp_synctty_ioctl,
	.poll	= ppp_sync_poll,
	.receive_buf = ppp_sync_receive,
	.write_wakeup = ppp_sync_wakeup,
};

static int __init
ppp_sync_init(void)
{
	int err;

	err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
	if (err != 0)
		printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
		       err);
	return err;
}

/*
 * The following routines provide the PPP channel interface.
 */
static int
ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
{
	struct syncppp *ap = chan->private;
	int err, val;
	u32 accm[8];
	void __user *argp = (void __user *)arg;
	u32 __user *p = argp;

	err = -EFAULT;
	switch (cmd) {
	case PPPIOCGFLAGS:
		val = ap->flags | ap->rbits;
		if (put_user(val, (int __user *) argp))
			break;
		err = 0;
		break;
	case PPPIOCSFLAGS:
		if (get_user(val, (int __user *) argp))
			break;
		ap->flags = val & ~SC_RCV_BITS;
		spin_lock_irq(&ap->recv_lock);
		ap->rbits = val & SC_RCV_BITS;
		spin_unlock_irq(&ap->recv_lock);
		err = 0;
		break;

	case PPPIOCGASYNCMAP:
		if (put_user(ap->xaccm[0], p))
			break;
		err = 0;
		break;
	case PPPIOCSASYNCMAP:
		if (get_user(ap->xaccm[0], p))
			break;
		err = 0;
		break;

	case PPPIOCGRASYNCMAP:
		if (put_user(ap->raccm, p))
			break;
		err = 0;
		break;
	case PPPIOCSRASYNCMAP:
		if (get_user(ap->raccm, p))
			break;
		err = 0;
		break;

	case PPPIOCGXASYNCMAP:
		if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
			break;
		err = 0;
		break;
	case PPPIOCSXASYNCMAP:
		if (copy_from_user(accm, argp, sizeof(accm)))
			break;
		accm[2] &= ~0x40000000U;	/* can't escape 0x5e */
		accm[3] |= 0x60000000U;		/* must escape 0x7d, 0x7e */
		memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
		err = 0;
		break;

	case PPPIOCGMRU:
		if (put_user(ap->mru, (int __user *) argp))
			break;
		err = 0;
		break;
	case PPPIOCSMRU:
		if (get_user(val, (int __user *) argp))
			break;
		if (val < PPP_MRU)
			val = PPP_MRU;
		ap->mru = val;
		err = 0;
		break;

	default:
		err = -ENOTTY;
	}
	return err;
}

/*
 * This is called at softirq level to deliver received packets
 * to the ppp_generic code, and to tell the ppp_generic code
 * if we can accept more output now.
 */
static void ppp_sync_process(unsigned long arg)
{
	struct syncppp *ap = (struct syncppp *) arg;
	struct sk_buff *skb;

	/* process received packets */
	while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
		if (skb->len == 0) {
			/* zero length buffers indicate error */
			ppp_input_error(&ap->chan, 0);
			kfree_skb(skb);
		}
		else
			ppp_input(&ap->chan, skb);
	}

	/* try to push more stuff out */
	if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
		ppp_output_wakeup(&ap->chan);
}

/*
 * Procedures for encapsulation and framing.
 */

static struct sk_buff*
ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
{
	int proto;
	unsigned char *data;
	int islcp;

	data  = skb->data;
	proto = get_unaligned_be16(data);

	/* LCP packets with codes between 1 (configure-request)
	 * and 7 (code-reject) must be sent as though no options
	 * have been negotiated.
	 */
	islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;

	/* compress protocol field if option enabled */
	if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
		skb_pull(skb,1);

	/* prepend address/control fields if necessary */
	if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
		if (skb_headroom(skb) < 2) {
			struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
			if (npkt == NULL) {
				kfree_skb(skb);
				return NULL;
			}
			skb_reserve(npkt,2);
			skb_copy_from_linear_data(skb,
				      skb_put(npkt, skb->len), skb->len);
			consume_skb(skb);
			skb = npkt;
		}
		skb_push(skb,2);
		skb->data[0] = PPP_ALLSTATIONS;
		skb->data[1] = PPP_UI;
	}

	ap->last_xmit = jiffies;

	if (skb && ap->flags & SC_LOG_OUTPKT)
		ppp_print_buffer ("send buffer", skb->data, skb->len);

	return skb;
}

/*
 * Transmit-side routines.
 */

/*
 * Send a packet to the peer over an sync tty line.
 * Returns 1 iff the packet was accepted.
 * If the packet was not accepted, we will call ppp_output_wakeup
 * at some later time.
 */
static int
ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb)
{
	struct syncppp *ap = chan->private;

	ppp_sync_push(ap);

	if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
		return 0;	/* already full */
	skb = ppp_sync_txmunge(ap, skb);
	if (skb != NULL)
		ap->tpkt = skb;
	else
		clear_bit(XMIT_FULL, &ap->xmit_flags);

	ppp_sync_push(ap);
	return 1;
}

/*
 * Push as much data as possible out to the tty.
 */
static int
ppp_sync_push(struct syncppp *ap)
{
	int sent, done = 0;
	struct tty_struct *tty = ap->tty;
	int tty_stuffed = 0;

	if (!spin_trylock_bh(&ap->xmit_lock))
		return 0;
	for (;;) {
		if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
			tty_stuffed = 0;
		if (!tty_stuffed && ap->tpkt) {
			set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
			sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
			if (sent < 0)
				goto flush;	/* error, e.g. loss of CD */
			if (sent < ap->tpkt->len) {
				tty_stuffed = 1;
			} else {
				consume_skb(ap->tpkt);
				ap->tpkt = NULL;
				clear_bit(XMIT_FULL, &ap->xmit_flags);
				done = 1;
			}
			continue;
		}
		/* haven't made any progress */
		spin_unlock_bh(&ap->xmit_lock);
		if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
		      (!tty_stuffed && ap->tpkt)))
			break;
		if (!spin_trylock_bh(&ap->xmit_lock))
			break;
	}
	return done;

flush:
	if (ap->tpkt) {
		kfree_skb(ap->tpkt);
		ap->tpkt = NULL;
		clear_bit(XMIT_FULL, &ap->xmit_flags);
		done = 1;
	}
	spin_unlock_bh(&ap->xmit_lock);
	return done;
}

/*
 * Flush output from our internal buffers.
 * Called for the TCFLSH ioctl.
 */
static void
ppp_sync_flush_output(struct syncppp *ap)
{
	int done = 0;

	spin_lock_bh(&ap->xmit_lock);
	if (ap->tpkt != NULL) {
		kfree_skb(ap->tpkt);
		ap->tpkt = NULL;
		clear_bit(XMIT_FULL, &ap->xmit_flags);
		done = 1;
	}
	spin_unlock_bh(&ap->xmit_lock);
	if (done)
		ppp_output_wakeup(&ap->chan);
}

/*
 * Receive-side routines.
 */

/* called when the tty driver has data for us.
 *
 * Data is frame oriented: each call to ppp_sync_input is considered
 * a whole frame. If the 1st flag byte is non-zero then the whole
 * frame is considered to be in error and is tossed.
 */
static void
ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
		char *flags, int count)
{
	struct sk_buff *skb;
	unsigned char *p;

	if (count == 0)
		return;

	if (ap->flags & SC_LOG_INPKT)
		ppp_print_buffer ("receive buffer", buf, count);

	/* stuff the chars in the skb */
	skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
	if (!skb) {
		printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
		goto err;
	}
	/* Try to get the payload 4-byte aligned */
	if (buf[0] != PPP_ALLSTATIONS)
		skb_reserve(skb, 2 + (buf[0] & 1));

	if (flags && *flags) {
		/* error flag set, ignore frame */
		goto err;
	} else if (count > skb_tailroom(skb)) {
		/* packet overflowed MRU */
		goto err;
	}

	p = skb_put(skb, count);
	memcpy(p, buf, count);

	/* strip address/control field if present */
	p = skb->data;
	if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
		/* chop off address/control */
		if (skb->len < 3)
			goto err;
		p = skb_pull(skb, 2);
	}

	/* decompress protocol field if compressed */
	if (p[0] & 1) {
		/* protocol is compressed */
		skb_push(skb, 1)[0] = 0;
	} else if (skb->len < 2)
		goto err;

	/* queue the frame to be processed */
	skb_queue_tail(&ap->rqueue, skb);
	return;

err:
	/* queue zero length packet as error indication */
	if (skb || (skb = dev_alloc_skb(0))) {
		skb_trim(skb, 0);
		skb_queue_tail(&ap->rqueue, skb);
	}
}

static void __exit
ppp_sync_cleanup(void)
{
	if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
		printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
}

module_init(ppp_sync_init);
module_exit(ppp_sync_cleanup);
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_SYNC_PPP);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* PPP synchronous tty channel driver for Linux.
	3	*
	4	* This is a ppp channel driver that can be used with tty device drivers
	5	* that are frame oriented, such as synchronous HDLC devices.
	6	*
	7	* Complete PPP frames without encoding/decoding are exchanged between
	8	* the channel driver and the device driver.
6aa20a22	9	*
1da177e4 LT	10	* The async map IOCTL codes are implemented to keep the user mode
	11	* applications happy if they call them. Synchronous PPP does not use
	12	* the async maps.
	13	*
	14	* Copyright 1999 Paul Mackerras.
	15	*
	16	* Also touched by the grubby hands of Paul Fulghum paulkf@microgate.com
	17	*
	18	* This program is free software; you can redistribute it and/or
	19	* modify it under the terms of the GNU General Public License
	20	* as published by the Free Software Foundation; either version
	21	* 2 of the License, or (at your option) any later version.
	22	*
	23	* This driver provides the encapsulation and framing for sending
	24	* and receiving PPP frames over sync serial lines. It relies on
	25	* the generic PPP layer to give it frames to send and to process
	26	* received frames. It implements the PPP line discipline.
	27	*
	28	* Part of the code in this driver was inspired by the old async-only
	29	* PPP driver, written by Michael Callahan and Al Longyear, and
	30	* subsequently hacked by Paul Mackerras.
	31	*
	32	* ==FILEVERSION 20040616==
	33	*/
	34
	35	#include <linux/module.h>
	36	#include <linux/kernel.h>
	37	#include <linux/skbuff.h>
	38	#include <linux/tty.h>
	39	#include <linux/netdevice.h>
	40	#include <linux/poll.h>
	41	#include <linux/ppp_defs.h>
4b32da2b	42	#include <linux/ppp-ioctl.h>
1da177e4 LT	43	#include <linux/ppp_channel.h>
1da177e4 LT	44	#include <linux/spinlock.h>
5e41fb83	45	#include <linux/completion.h>
1da177e4	46	#include <linux/init.h>
a6b7a407	47	#include <linux/interrupt.h>
5a0e3ad6	48	#include <linux/slab.h>
96545aeb	49	#include <asm/unaligned.h>
1da177e4	50	#include <asm/uaccess.h>
1da177e4 LT	51
	52	#define PPP_VERSION "2.4.2"
	53
	54	/* Structure for storing local state. */
	55	struct syncppp {
	56	struct tty_struct *tty;
	57	unsigned int flags;
	58	unsigned int rbits;
	59	int mru;
	60	spinlock_t xmit_lock;
	61	spinlock_t recv_lock;
	62	unsigned long xmit_flags;
	63	u32 xaccm[8];
	64	u32 raccm;
	65	unsigned int bytes_sent;
	66	unsigned int bytes_rcvd;
	67
	68	struct sk_buff *tpkt;
	69	unsigned long last_xmit;
	70
	71	struct sk_buff_head rqueue;
	72
	73	struct tasklet_struct tsk;
	74
	75	atomic_t refcnt;
5e41fb83	76	struct completion dead_cmp;
1da177e4 LT	77	struct ppp_channel chan; /* interface to generic ppp layer */
	78	};
	79
	80	/* Bit numbers in xmit_flags */
	81	#define XMIT_WAKEUP 0
	82	#define XMIT_FULL 1
	83
	84	/* Bits in rbits */
	85	#define SC_RCV_BITS (SC_RCV_B7_1\|SC_RCV_B7_0\|SC_RCV_ODDP\|SC_RCV_EVNP)
	86
	87	#define PPPSYNC_MAX_RQLEN 32 /* arbitrary */
	88
	89	/*
	90	* Prototypes.
	91	*/
	92	static struct sk_buff* ppp_sync_txmunge(struct syncppp ap, struct sk_buff );
	93	static int ppp_sync_send(struct ppp_channel chan, struct sk_buff skb);
	94	static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
	95	unsigned long arg);
	96	static void ppp_sync_process(unsigned long arg);
	97	static int ppp_sync_push(struct syncppp *ap);
	98	static void ppp_sync_flush_output(struct syncppp *ap);
	99	static void ppp_sync_input(struct syncppp ap, const unsigned char buf,
	100	char *flags, int count);
	101
d7100da0	102	static const struct ppp_channel_ops sync_ops = {
	103	.start_xmit = ppp_sync_send,
	104	.ioctl = ppp_sync_ioctl,
1da177e4 LT	105	};
	106
	107	/*
167bfa71	108	* Utility procedure to print a buffer in hex/ascii
1da177e4	109	*/
1da177e4 LT	110	static void
	111	ppp_print_buffer (const char name, const __u8 buf, int count)
	112	{
1da177e4 LT	113	if (name != NULL)
	114	printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);
	115
167bfa71	116	print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, count);
1da177e4 LT	117	}
	118
	119
	120	/*
	121	* Routines implementing the synchronous PPP line discipline.
	122	*/
	123
	124	/*
	125	* We have a potential race on dereferencing tty->disc_data,
	126	* because the tty layer provides no locking at all - thus one
	127	* cpu could be running ppp_synctty_receive while another
	128	* calls ppp_synctty_close, which zeroes tty->disc_data and
	129	* frees the memory that ppp_synctty_receive is using. The best
	130	* way to fix this is to use a rwlock in the tty struct, but for now
	131	* we use a single global rwlock for all ttys in ppp line discipline.
	132	*
25985edc	133	* FIXME: Fixed in tty_io nowadays.
1da177e4 LT	134	*/
	135	static DEFINE_RWLOCK(disc_data_lock);
	136
	137	static struct syncppp sp_get(struct tty_struct tty)
	138	{
	139	struct syncppp *ap;
	140
	141	read_lock(&disc_data_lock);
	142	ap = tty->disc_data;
	143	if (ap != NULL)
	144	atomic_inc(&ap->refcnt);
	145	read_unlock(&disc_data_lock);
	146	return ap;
	147	}
	148
	149	static void sp_put(struct syncppp *ap)
	150	{
	151	if (atomic_dec_and_test(&ap->refcnt))
5e41fb83	152	complete(&ap->dead_cmp);
1da177e4 LT	153	}
	154
	155	/*
	156	* Called when a tty is put into sync-PPP line discipline.
	157	*/
	158	static int
	159	ppp_sync_open(struct tty_struct *tty)
	160	{
	161	struct syncppp *ap;
	162	int err;
9c705260	163	int speed;
1da177e4	164
f34d7a5b AC	165	if (tty->ops->write == NULL)
	166	return -EOPNOTSUPP;
	167
dd00cc48	168	ap = kzalloc(sizeof(*ap), GFP_KERNEL);
1da177e4	169	err = -ENOMEM;
cd228d54	170	if (!ap)
1da177e4 LT	171	goto out;
	172
	173	/* initialize the syncppp structure */
1da177e4 LT	174	ap->tty = tty;
	175	ap->mru = PPP_MRU;
	176	spin_lock_init(&ap->xmit_lock);
	177	spin_lock_init(&ap->recv_lock);
	178	ap->xaccm[0] = ~0U;
	179	ap->xaccm[3] = 0x60000000U;
	180	ap->raccm = ~0U;
	181
	182	skb_queue_head_init(&ap->rqueue);
	183	tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);
	184
	185	atomic_set(&ap->refcnt, 1);
5e41fb83	186	init_completion(&ap->dead_cmp);
1da177e4 LT	187
	188	ap->chan.private = ap;
	189	ap->chan.ops = &sync_ops;
	190	ap->chan.mtu = PPP_MRU;
	191	ap->chan.hdrlen = 2; /* for A/C bytes */
9c705260 GP	192	speed = tty_get_baud_rate(tty);
9c705260 GP	193	ap->chan.speed = speed;
1da177e4 LT	194	err = ppp_register_channel(&ap->chan);
	195	if (err)
	196	goto out_free;
	197
	198	tty->disc_data = ap;
33f0f88f	199	tty->receive_room = 65536;
1da177e4 LT	200	return 0;
	201
	202	out_free:
	203	kfree(ap);
	204	out:
	205	return err;
	206	}
	207
	208	/*
	209	* Called when the tty is put into another line discipline
	210	* or it hangs up. We have to wait for any cpu currently
	211	* executing in any of the other ppp_synctty_* routines to
	212	* finish before we can call ppp_unregister_channel and free
	213	* the syncppp struct. This routine must be called from
	214	* process context, not interrupt or softirq context.
	215	*/
	216	static void
	217	ppp_sync_close(struct tty_struct *tty)
	218	{
	219	struct syncppp *ap;
	220
	221	write_lock_irq(&disc_data_lock);
	222	ap = tty->disc_data;
	223	tty->disc_data = NULL;
	224	write_unlock_irq(&disc_data_lock);
cd228d54	225	if (!ap)
1da177e4 LT	226	return;
	227
	228	/*
	229	* We have now ensured that nobody can start using ap from now
	230	* on, but we have to wait for all existing users to finish.
	231	* Note that ppp_unregister_channel ensures that no calls to
	232	* our channel ops (i.e. ppp_sync_send/ioctl) are in progress
	233	* by the time it returns.
	234	*/
	235	if (!atomic_dec_and_test(&ap->refcnt))
5e41fb83	236	wait_for_completion(&ap->dead_cmp);
1da177e4 LT	237	tasklet_kill(&ap->tsk);
	238
	239	ppp_unregister_channel(&ap->chan);
	240	skb_queue_purge(&ap->rqueue);
1d2f8c95	241	kfree_skb(ap->tpkt);
1da177e4 LT	242	kfree(ap);
	243	}
	244
	245	/*
	246	* Called on tty hangup in process context.
	247	*
	248	* Wait for I/O to driver to complete and unregister PPP channel.
	249	* This is already done by the close routine, so just call that.
	250	*/
	251	static int ppp_sync_hangup(struct tty_struct *tty)
	252	{
	253	ppp_sync_close(tty);
	254	return 0;
	255	}
	256
	257	/*
	258	* Read does nothing - no data is ever available this way.
	259	* Pppd reads and writes packets via /dev/ppp instead.
	260	*/
	261	static ssize_t
	262	ppp_sync_read(struct tty_struct tty, struct file file,
	263	unsigned char __user *buf, size_t count)
	264	{
	265	return -EAGAIN;
	266	}
	267
	268	/*
	269	* Write on the tty does nothing, the packets all come in
	270	* from the ppp generic stuff.
	271	*/
	272	static ssize_t
	273	ppp_sync_write(struct tty_struct tty, struct file file,
	274	const unsigned char *buf, size_t count)
	275	{
	276	return -EAGAIN;
	277	}
	278
	279	static int
	280	ppp_synctty_ioctl(struct tty_struct tty, struct file file,
	281	unsigned int cmd, unsigned long arg)
	282	{
	283	struct syncppp *ap = sp_get(tty);
	284	int __user p = (int __user )arg;
	285	int err, val;
	286
cd228d54	287	if (!ap)
1da177e4 LT	288	return -ENXIO;
	289	err = -EFAULT;
	290	switch (cmd) {
	291	case PPPIOCGCHAN:
1da177e4 LT	292	err = -EFAULT;
	293	if (put_user(ppp_channel_index(&ap->chan), p))
	294	break;
	295	err = 0;
	296	break;
	297
	298	case PPPIOCGUNIT:
1da177e4 LT	299	err = -EFAULT;
	300	if (put_user(ppp_unit_number(&ap->chan), p))
	301	break;
	302	err = 0;
	303	break;
	304
1da177e4 LT	305	case TCFLSH:
	306	/* flush our buffers and the serial port's buffer */
	307	if (arg == TCIOFLUSH \|\| arg == TCOFLUSH)
	308	ppp_sync_flush_output(ap);
e7f3880c	309	err = n_tty_ioctl_helper(tty, file, cmd, arg);
1da177e4 LT	310	break;
	311
	312	case FIONREAD:
	313	val = 0;
	314	if (put_user(val, p))
	315	break;
	316	err = 0;
	317	break;
	318
	319	default:
d0127539 AC	320	err = tty_mode_ioctl(tty, file, cmd, arg);
d0127539 AC	321	break;
1da177e4 LT	322	}
	323
	324	sp_put(ap);
	325	return err;
	326	}
	327
	328	/* No kernel lock - fine */
	329	static unsigned int
	330	ppp_sync_poll(struct tty_struct tty, struct file file, poll_table *wait)
	331	{
	332	return 0;
	333	}
	334
92d326f6	335	/* May sleep, don't call from interrupt level or with interrupts disabled */
55db4c64	336	static void
1da177e4 LT	337	ppp_sync_receive(struct tty_struct tty, const unsigned char buf,
	338	char *cflags, int count)
	339	{
	340	struct syncppp *ap = sp_get(tty);
	341	unsigned long flags;
	342
cd228d54	343	if (!ap)
55db4c64	344	return;
1da177e4 LT	345	spin_lock_irqsave(&ap->recv_lock, flags);
	346	ppp_sync_input(ap, buf, cflags, count);
	347	spin_unlock_irqrestore(&ap->recv_lock, flags);
b03efcfb	348	if (!skb_queue_empty(&ap->rqueue))
1da177e4 LT	349	tasklet_schedule(&ap->tsk);
1da177e4 LT	350	sp_put(ap);
4a21b8cb	351	tty_unthrottle(tty);
1da177e4 LT	352	}
	353
	354	static void
	355	ppp_sync_wakeup(struct tty_struct *tty)
	356	{
	357	struct syncppp *ap = sp_get(tty);
	358
	359	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
cd228d54	360	if (!ap)
1da177e4 LT	361	return;
	362	set_bit(XMIT_WAKEUP, &ap->xmit_flags);
	363	tasklet_schedule(&ap->tsk);
	364	sp_put(ap);
	365	}
	366
	367
a352def2	368	static struct tty_ldisc_ops ppp_sync_ldisc = {
1da177e4 LT	369	.owner = THIS_MODULE,
	370	.magic = TTY_LDISC_MAGIC,
	371	.name = "pppsync",
	372	.open = ppp_sync_open,
	373	.close = ppp_sync_close,
	374	.hangup = ppp_sync_hangup,
	375	.read = ppp_sync_read,
	376	.write = ppp_sync_write,
	377	.ioctl = ppp_synctty_ioctl,
	378	.poll = ppp_sync_poll,
1da177e4 LT	379	.receive_buf = ppp_sync_receive,
	380	.write_wakeup = ppp_sync_wakeup,
	381	};
	382
	383	static int __init
	384	ppp_sync_init(void)
	385	{
	386	int err;
	387
	388	err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
	389	if (err != 0)
	390	printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
	391	err);
	392	return err;
	393	}
	394
	395	/*
	396	* The following routines provide the PPP channel interface.
	397	*/
	398	static int
	399	ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
	400	{
	401	struct syncppp *ap = chan->private;
	402	int err, val;
	403	u32 accm[8];
	404	void __user argp = (void __user )arg;
	405	u32 __user *p = argp;
	406
	407	err = -EFAULT;
	408	switch (cmd) {
	409	case PPPIOCGFLAGS:
	410	val = ap->flags \| ap->rbits;
	411	if (put_user(val, (int __user *) argp))
	412	break;
	413	err = 0;
	414	break;
	415	case PPPIOCSFLAGS:
	416	if (get_user(val, (int __user *) argp))
	417	break;
	418	ap->flags = val & ~SC_RCV_BITS;
	419	spin_lock_irq(&ap->recv_lock);
	420	ap->rbits = val & SC_RCV_BITS;
	421	spin_unlock_irq(&ap->recv_lock);
	422	err = 0;
	423	break;
	424
	425	case PPPIOCGASYNCMAP:
	426	if (put_user(ap->xaccm[0], p))
	427	break;
	428	err = 0;
	429	break;
	430	case PPPIOCSASYNCMAP:
	431	if (get_user(ap->xaccm[0], p))
	432	break;
	433	err = 0;
	434	break;
	435
	436	case PPPIOCGRASYNCMAP:
	437	if (put_user(ap->raccm, p))
	438	break;
	439	err = 0;
	440	break;
	441	case PPPIOCSRASYNCMAP:
	442	if (get_user(ap->raccm, p))
443	break;
444	err = 0;
445	break;
446
447	case PPPIOCGXASYNCMAP:
448	if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
449	break;
450	err = 0;
451	break;
452	case PPPIOCSXASYNCMAP:
453	if (copy_from_user(accm, argp, sizeof(accm)))
454	break;
455	accm[2] &= ~0x40000000U; /* can't escape 0x5e */
456	accm[3] \|= 0x60000000U; /* must escape 0x7d, 0x7e */
457	memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
458	err = 0;
459	break;
460
461	case PPPIOCGMRU:
462	if (put_user(ap->mru, (int __user *) argp))
463	break;
464	err = 0;
465	break;
466	case PPPIOCSMRU:
467	if (get_user(val, (int __user *) argp))
468	break;
469	if (val < PPP_MRU)
470	val = PPP_MRU;
471	ap->mru = val;
472	err = 0;
473	break;
474
475	default:
476	err = -ENOTTY;
477	}
478	return err;
479	}
480
481	/*
482	* This is called at softirq level to deliver received packets
483	* to the ppp_generic code, and to tell the ppp_generic code
484	* if we can accept more output now.
485	*/
486	static void ppp_sync_process(unsigned long arg)
487	{
488	struct syncppp ap = (struct syncppp ) arg;
489	struct sk_buff *skb;
490
491	/* process received packets */
492	while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
493	if (skb->len == 0) {
494	/* zero length buffers indicate error */
495	ppp_input_error(&ap->chan, 0);
496	kfree_skb(skb);
497	}
498	else
499	ppp_input(&ap->chan, skb);
500	}
501
502	/* try to push more stuff out */
503	if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
504	ppp_output_wakeup(&ap->chan);
505	}
506
507	/*
508	* Procedures for encapsulation and framing.
509	*/
510
3c582b30	511	static struct sk_buff*
1da177e4 LT	512	ppp_sync_txmunge(struct syncppp ap, struct sk_buff skb)
	513	{
	514	int proto;
	515	unsigned char *data;
	516	int islcp;
	517
	518	data = skb->data;
96545aeb	519	proto = get_unaligned_be16(data);
1da177e4 LT	520
	521	/* LCP packets with codes between 1 (configure-request)
	522	* and 7 (code-reject) must be sent as though no options
	523	* have been negotiated.
	524	*/
	525	islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
	526
	527	/* compress protocol field if option enabled */
	528	if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
	529	skb_pull(skb,1);
	530
	531	/* prepend address/control fields if necessary */
	532	if ((ap->flags & SC_COMP_AC) == 0 \|\| islcp) {
	533	if (skb_headroom(skb) < 2) {
	534	struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
	535	if (npkt == NULL) {
	536	kfree_skb(skb);
	537	return NULL;
	538	}
	539	skb_reserve(npkt,2);
d626f62b ACM	540	skb_copy_from_linear_data(skb,
d626f62b ACM	541	skb_put(npkt, skb->len), skb->len);
968d7018	542	consume_skb(skb);
1da177e4 LT	543	skb = npkt;
	544	}
	545	skb_push(skb,2);
	546	skb->data[0] = PPP_ALLSTATIONS;
	547	skb->data[1] = PPP_UI;
	548	}
	549
	550	ap->last_xmit = jiffies;
	551
	552	if (skb && ap->flags & SC_LOG_OUTPKT)
	553	ppp_print_buffer ("send buffer", skb->data, skb->len);
	554
	555	return skb;
	556	}
	557
	558	/*
	559	* Transmit-side routines.
	560	*/
	561
	562	/*
	563	* Send a packet to the peer over an sync tty line.
	564	* Returns 1 iff the packet was accepted.
	565	* If the packet was not accepted, we will call ppp_output_wakeup
	566	* at some later time.
	567	*/
	568	static int
	569	ppp_sync_send(struct ppp_channel chan, struct sk_buff skb)
	570	{
	571	struct syncppp *ap = chan->private;
	572
	573	ppp_sync_push(ap);
	574
	575	if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
	576	return 0; /* already full */
	577	skb = ppp_sync_txmunge(ap, skb);
	578	if (skb != NULL)
	579	ap->tpkt = skb;
	580	else
	581	clear_bit(XMIT_FULL, &ap->xmit_flags);
	582
	583	ppp_sync_push(ap);
	584	return 1;
	585	}
	586
	587	/*
	588	* Push as much data as possible out to the tty.
	589	*/
	590	static int
	591	ppp_sync_push(struct syncppp *ap)
	592	{
	593	int sent, done = 0;
	594	struct tty_struct *tty = ap->tty;
	595	int tty_stuffed = 0;
	596
	597	if (!spin_trylock_bh(&ap->xmit_lock))
	598	return 0;
	599	for (;;) {
	600	if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
	601	tty_stuffed = 0;
cd228d54	602	if (!tty_stuffed && ap->tpkt) {
1da177e4	603	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
f34d7a5b	604	sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
1da177e4 LT	605	if (sent < 0)
	606	goto flush; /* error, e.g. loss of CD */
	607	if (sent < ap->tpkt->len) {
	608	tty_stuffed = 1;
	609	} else {
968d7018	610	consume_skb(ap->tpkt);
1da177e4 LT	611	ap->tpkt = NULL;
	612	clear_bit(XMIT_FULL, &ap->xmit_flags);
	613	done = 1;
	614	}
	615	continue;
	616	}
	617	/* haven't made any progress */
	618	spin_unlock_bh(&ap->xmit_lock);
8e95a202 JP	619	if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) \|\|
8e95a202 JP	620	(!tty_stuffed && ap->tpkt)))
1da177e4 LT	621	break;
	622	if (!spin_trylock_bh(&ap->xmit_lock))
	623	break;
	624	}
	625	return done;
	626
	627	flush:
cd228d54	628	if (ap->tpkt) {
1da177e4 LT	629	kfree_skb(ap->tpkt);
	630	ap->tpkt = NULL;
	631	clear_bit(XMIT_FULL, &ap->xmit_flags);
	632	done = 1;
	633	}
	634	spin_unlock_bh(&ap->xmit_lock);
	635	return done;
	636	}
	637
	638	/*
	639	* Flush output from our internal buffers.
	640	* Called for the TCFLSH ioctl.
	641	*/
	642	static void
	643	ppp_sync_flush_output(struct syncppp *ap)
	644	{
	645	int done = 0;
	646
	647	spin_lock_bh(&ap->xmit_lock);
	648	if (ap->tpkt != NULL) {
	649	kfree_skb(ap->tpkt);
	650	ap->tpkt = NULL;
	651	clear_bit(XMIT_FULL, &ap->xmit_flags);
	652	done = 1;
	653	}
	654	spin_unlock_bh(&ap->xmit_lock);
	655	if (done)
	656	ppp_output_wakeup(&ap->chan);
	657	}
	658
	659	/*
	660	* Receive-side routines.
	661	*/
	662
	663	/* called when the tty driver has data for us.
	664	*
	665	* Data is frame oriented: each call to ppp_sync_input is considered
	666	* a whole frame. If the 1st flag byte is non-zero then the whole
	667	* frame is considered to be in error and is tossed.
	668	*/
	669	static void
	670	ppp_sync_input(struct syncppp ap, const unsigned char buf,
	671	char *flags, int count)
	672	{
	673	struct sk_buff *skb;
	674	unsigned char *p;
	675
	676	if (count == 0)
	677	return;
	678
	679	if (ap->flags & SC_LOG_INPKT)
	680	ppp_print_buffer ("receive buffer", buf, count);
	681
	682	/* stuff the chars in the skb */
cd228d54 JP	683	skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
cd228d54 JP	684	if (!skb) {
1da177e4 LT	685	printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
	686	goto err;
	687	}
	688	/* Try to get the payload 4-byte aligned */
	689	if (buf[0] != PPP_ALLSTATIONS)
	690	skb_reserve(skb, 2 + (buf[0] & 1));
	691
cd228d54	692	if (flags && *flags) {
1da177e4 LT	693	/* error flag set, ignore frame */
	694	goto err;
	695	} else if (count > skb_tailroom(skb)) {
	696	/* packet overflowed MRU */
	697	goto err;
	698	}
	699
	700	p = skb_put(skb, count);
	701	memcpy(p, buf, count);
	702
	703	/* strip address/control field if present */
	704	p = skb->data;
	705	if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
	706	/* chop off address/control */
	707	if (skb->len < 3)
	708	goto err;
	709	p = skb_pull(skb, 2);
	710	}
	711
	712	/* decompress protocol field if compressed */
	713	if (p[0] & 1) {
	714	/* protocol is compressed */
	715	skb_push(skb, 1)[0] = 0;
	716	} else if (skb->len < 2)
	717	goto err;
	718
	719	/* queue the frame to be processed */
	720	skb_queue_tail(&ap->rqueue, skb);
	721	return;
	722
	723	err:
	724	/* queue zero length packet as error indication */
	725	if (skb \|\| (skb = dev_alloc_skb(0))) {
	726	skb_trim(skb, 0);
	727	skb_queue_tail(&ap->rqueue, skb);
	728	}
	729	}
	730
	731	static void __exit
	732	ppp_sync_cleanup(void)
	733	{
64ccd715	734	if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
1da177e4 LT	735	printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
	736	}
	737
	738	module_init(ppp_sync_init);
	739	module_exit(ppp_sync_cleanup);
	740	MODULE_LICENSE("GPL");
	741	MODULE_ALIAS_LDISC(N_SYNC_PPP);